<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .container {
            display: grid;
            grid-template-columns: 200px 1fr;
        }
    </style>
</head>

<body>
    <div class="container">
        <div class="left" style="background-color:blue;height:100px;"></div>
        <div class="right" style="background-color:green;height:100px;"></div>
    </div>
</body>

</html>